The private-equity firm's IPO is a hit, but don't expect another Google. Here, the true winners are CEO Stephen Schwarzman and his partners. Is this the top of the buyout boon?

BLACKSTONE'S INITIAL PUBLIC OFFERING Thursday marked the most important debut for any company since Google went public in 2004. Just as Google changed the rules of the game in Internet search and dealt a sharp blow to newspapers and other traditional media, the Blackstone Group, the world's most prominent private-equity firm, is reshaping the corporate landscape and helping to fuel a global bull market in stocks through its appetite for leveraged buyouts.

Blackstone isn't another Google, however, and is unlikely to see its...